The role of stress in suppressing immune function has received considerable attention due to the obvious implications regarding disease in general and cancer more specifically. Most stress research has emphasized physical aspects of the stressor with little regard for psychological dimensions. Herein, it is hypothesized that availability of psychological coping strategies, such as control over the termination of an aversive event, may be a critical factor in mitigating against the effects of exposure to a stressor on immune function. This will be tested using a animal model, the learned helplessness paradigm. Specifically, rats will be exposed to escapable or inescapable aversive events and measures of immunocompetence will be assessed. These measures will include in vitro lymphocyte proliferation in response to mitogenic stimulation and in vivo generation of specific antibodies to an antigen. An important aspect of this project is to plot the time course and long term effects of prior experience with controllable or uncontrollable events. Secondly, potential involvement of corticosteroids and endogenous opiates will be investigated in adrenalectomized or naltrexone-treated subjects. We are requesting support in order to obtain necessary pilot data before a major comprehensive research proposal can be submitted. This project has important implications.concerning the role of behavioral control over stressors, a feature receiving little or no attention in previous work, and directions for future research regarding possible mechanisms of immunosuppression associated with ineffective coping strategies.